A day after the acting Homeland Security secretary estimated that more than 1 percent of the populations of Guatemala and Honduras had entered the U.S. since September, President Trump declared an “invasion” at the U.S.-Mexico border.

Meanwhile, his administration expects record numbers of migrants to arrive from Central America in the coming months.

"When you see these caravans starting out with 20,000 people, that's an invasion,” Trump said at his Wednesday evening “Make American Great Again” rally in Panama City, Fla., defending his declaration of a national emergency at the border earlier this year. “No nation can tolerate a massive organized violation of its immigration laws. And no one should run for office without an ironclad pledge to protect and defend America's borders."

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The White House recently proposed charging asylum-seekers a fee to process their applications in an effort to crack down on the surge of Central American migrants trying to cross into the U.S.

In a speech Tuesday to the 49th Washington Conference of the Americas, acting Homeland Security Secretary Kevin McAleenan described why most migrants arriving at the U.S. border come from Guatemala, Honduras or El Salvador.

“Guatemala and Honduras have seen over 1 percent of their total population migrate to the U.S. in the first seven months of this fiscal year,” McAleenan said, citing government-funded research completed by Vanderbilt University. He said most migrants come to escape extreme poverty and stay because of a flawed U.S. immigration system.

Acting-Homeland Security Secretary Kevin McAleenan prepares for a House Appropriations subcommittee hearing on his agency's future funding, on Capitol Hill in Washington, April 30, 2019. (Associated Press)

“One department of Guatemala, Huehuetenango, has seen almost 35,000 of its residents — close to 3 percent of the population — migrate to the U.S. in that time frame,” McAleenan added.

The flawed U.S. immigration system often permits families and unaccompanied minors to live in the United States for months or years as their asylum claims are processed, even though most will never obtain legal status. Central Americans notice family or neighbors leave and successfully make it into the U.S., so they too choose to embark on the journey, the DHS chief explained.

“In March, we had over 103,000 irregular arrivals of undocumented migrants — 90 percent crossing the U.S. border unlawfully and unsafely in the hands of human smugglers. We will see similar numbers in April,” McAleenan continued, explaining that he expects current trends to continue in the upcoming months.

According to the study carried out by Vanderbilt’s Latin American Public Opinion Project in Guatemala earlier this year, 1 in 4 Guatemalans intend to migrate from Guatemala, with 85 percent of them indicating the U.S. as their preferred destination.

“That’s over 4 million Guatemalans who intend to migrate to the United States,” McAleenan said. The DHS head is working with Jared Kushner, the president’s son-in-law and senior adviser, on an immigration bill designed to overhaul the legal immigration system, the Washington Post reported.

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The proposed legislation will include “an aggressive and holistic strategy” to work together with Central America officials in order to identify “pushes” that drive migrants out of Central America.

“We want to work closely with all three countries' customs administrations to help increase the efficiency of cross-border trade by reducing supply chain barriers and support exports and job creation," McAleenan said Tuesday, according to the Washington Examiner. "From an infrastructure, technology, automation, and legal perspective, DHS’s Customs and Border Protection is pursuing broad support for the region’s customs administrations to modernize practices in all of these areas.”

Fox News' Victor Garcia contributed to this report.